1. Field of the Invention
The present invention pertains to ordinance. With greater particularity, the present invention pertains to munition rounds for hyper-velocity guns. With greatest particularity, the present invention pertains to a munition round which has a multi-part, sequentially fired traveling charge which maintains a longer duration high pressure impulse on the projectile while in the gun barrel than conventional breech fired charges.
2. Description of the Prior Art
The art of munitions is old and well developed. Gun systems typically include a tubular barrel having a bore and a sealed breech wherein a propellant charge is positioned. A projectile is placed in the bore of the barrel and against the propellant charge at the breech end of the gun barrel. When the gun is fired, the propellant is ignited to generate a large volume of high pressure gas. This pressure acts against the bore and sealed breech and against the base of the projectile. This unbalanced pressure on the projectile base causes an unbalanced force which accelerates the projectile toward the muzzle end of the gun barrel. The projectile achieves a high velocity as it reaches the muzzle and it continues out of the gun barrel and traverses a ballistic trajectory to the target.
There have been many attempts to increase the muzzle velocity of a projectile by modifying or tailoring the propellant charge to produce a more constant pressure impulse on the base of the projectile while it is traversing the barrel bore. If the projectile is considered to be a piston and if the propellant charge burns fast enough to be completely consumed before the projectile has moved far from the breech, then it may be seen that the chamber pressure initially increases rapidly to a maximum. From the point the propellant is completely consumed, as the projectile continues to move toward the muzzle, the confined volume behind the projectile increases, leading to a rapid decrease in pressure on the base of the projectile. Obviously, the higher the average pressure accelerating the projectile during the time the projectile is in the barrel, the higher the muzzle velocity will be, all other factors being equal.
Typical of attempts to tailor chamber pressure has been the staging or sequential ignition of multiple propellant charges in the breech of the gun while the projectile moves through the bore, and as the confined volume behind the projectile increases.
One such attempt placed multiple charges in the breech in stacked fashion, adjacent charges being linked by a coiled cable which is attached to a ball projectile. As the first charge is fired, the ball begins moving down the barrel and trailing the cable. At the limit of the first cable coil, the cable begins to tear into the second charge, exposing it to the hot gases produced when the first charge was fired. This process continues until the last charge is fired just prior to the ball reaching the muzzle. This scheme is said to produce a higher average pressure on the ball projectile while it is in the barrel as compared to a single breech charge, and results in a higher muzzle velocity. Although the cable moves with the ball, the charges do not, and so this cannot be said to be a traveling charge.
All breech charges are limited in their ability to maintain a significant pressure on the projectile base by the expansion rate of the propelling gas which limits the pressure which it can apply to the projectile, and the need to accelerate the whole of the breech charge gas to half the velocity of the projectile, which consumes much energy.
Another attempt to increase muzzle velocity of a gun fired projectile in a rifled gun involved a cartridge which was attached to a projectile and had a series of rear facing propellant containing cups stacked behind the projectile in a shell. The base of each cup had a passageway for hot gases which communicated with the next cup. The passageway could be angled or coiled to delay ignition of the next charge to allow the projectile to move to an optimum position for subsequent charge ignition. The first charge accelerated the projectile and remaining cups. Periodically, another propellant charge would ignite and supply additional high pressure gas behind the projectile. This scheme differed from the one discussed above in that here the unignited propellant charges moved with the projectile instead of remaining in the breech. Thus, this attempt did constitute a traveling charge.
Yet another attempt to solve the projectile muzzle velocity problem involved placing a second propellant charge within the projectile and firing that second charge when the projectile is at an intermediate position in its travel down the barrel, at the moment of maximum gas pressure.
Other attempts to solve this problem have included using a second charge in the breech to fire a piston which compresses gases at the base of the projectile to thereby increase the average pressure-time impulse acting on the projectile base and cause the projectile to reach a higher muzzle velocity.
One prior art projectile used a series of stages to provide additional impulses during the flight of the projectile after leaving the muzzle. Still another approach used multiple charges and hot gas passageways to control ignition timing of the respective charges. Yet another approach involved using a shaped projectile and a series of explosive charges to accelerate the projectile by triggering the charges to explode just as the curved aft portion of the projectile passes pre-designated points while traversing the barrel bore.
Current attempts to develop the traveling charge for high velocity guns usually utilize a cigarette burn type charge which burns only on the rear face of the propellant at ever increasing burn rate to sustain pressure on the base of the projectile. Several problems have been encountered with a cigarette burn approach, such as:
(a) Burn rate and base pressure are limited by the tendency of the propellant to explode if its break-up is induced by excessive stress. PA1 (b) Since the cigarette burn requires an increasing burn-rate as the traveling charge moves down the bore, the charge must be carefully tailored to contain increasing proportions of high burn rate propellant which is expensive and requires much development to maintain stable burning and obtain optimum velocity. PA1 (c) High burn rate propellants are difficult to handle safely under field conditions. PA1 (d) Experimental experience is limited to comparatively small bores and may not be confidently extrapolated to large bores without risk of propellant break-up and detonation. PA1 (e) Once a cigarette burn traveling charge is tailored it is only suitable for one muzzle velocity.
Prior attempts to increase muzzle velocity have been limited in effectiveness by the mechanical or pyrotechnic means used to time firing of the sequential charges. These mechanical or pyrotechnic devices are notoriously inaccurate and unreliable when called upon to control the timing of charges that must be fired within milliseconds or microseconds of one another. Unless the charges are fired in a precise timed sequence, the optimum muzzle velocity will not be attained.
A further problem in the prior art is that even if prior devices were able to produce the desired muzzle velocities, the construction of the projectile and the traveling charge is such that they must withstand the full stresses caused by setback forces in the contained propellant or high explosive due to projectile acceleration and the centrifugal and torque forces generated by engagement with rifling in the gun bore as the gun is fired and the rifling begins to revolve the projectile to a high rate of rotation. The added structural mass of the projectile to enable it to withstand these high stresses greatly limits the amount of propellant and explosive payload the projectile can carry (to about 10% of its overall mass). This greatly increases the pressure required to accelerate it to achieve the stated muzzle velocity which increases the weight of the projectile and the gun barrel and limits the destructive power of the projectile.